This application includes a microfiche appendix including one microfiche and 20 frames.
The present invention relates to an ultrasonic system for measuring the distance between a sensor and a surface.
Various systems have been proposed for measuring the distance between a vehicle or machine part and the ground over which it moves. This is desired in order to adjust the position of working tools or implements with respect to the terrain or soil surface. One such system is described in Australian Petty Patent Abridgement No. AU-A-78449/87, published 10 March 1988 wherein distance to the soil is measured by reflecting an ultrasonic signal off the soil surface. Variations in soil condition and type are compensated for by deriving the distance to the soil surface by averaging the leading and trailing edge times of an amplitude envelope of an echo signal reflected by the soil surface. However, this and other similar systems have not been able to function accurately in conditions where crops or trash lie on top of the ground surface. Accordingly, a distance or height sensing system which can distinguish between crop or trash and soil surface is desired.